1. Field of the Invention
The present invention relates to rails for motor vehicles and, more particularly, to an impact reinforcement for curved rails in motor vehicles.
2. Description of the Related Art
Motor vehicles typically include one or more impact energy absorbing members to absorb energy of an impact. In the motor vehicle, the impact energy absorbing members are usually longitudinal rails of the motor vehicle. For a frontal impact on the motor vehicle, longitudinal front rails act as main impact energy absorbing members. The front rails are closed section rails which generally stop at a dash or instrument panel and taper to sills and underbody rail extensions through a member referred to as a "torque box".
As these motor vehicles become smaller and move toward a more "cab forward" design, the length of available crush space for a frontal impact decreases. The result is less crush space to absorb the same amount of energy. At the same time, the impact requirements governed by law are moving toward higher speed protection as well as partial or offset barrier impacts, both of which substantially increase the amount of energy the motor vehicle must absorb. As a result, the front rails must be designed to absorb more energy during a frontal impact.
The front rails typically extend from the dash panel/sill area straight to or into a bumper of the motor vehicle. A straight section which is designed to crush axially is the most efficient method of energy absorption. Unfortunately, straight front rails are not always possible due to several factors, the major of which is engine and transmission packaging. Under these circumstances, the only alternative is to curve the front rails up and over interfering engine and transmission points.
One disadvantage of curved front rails is that the geometry results in a bending mode of the front rails rather than a preferred axial crush mode. Thus, there is a need in the art to increase the bending strength of curved front rails to allow crush in an axial mode before a bending mode.